Flush contact step attenuator for coaxial circuits



9 1970 H. BACHER 3556,@

FLUSH CONTACT STEP ATTENUATOR FOR COAXIAL CIRCUITS Filed March 29, 19683 Sheets-Sheet 1 INVENTOR Helmuf Bacher BY W ATTORNEY Dec. 22, 1970 H.BACHER FLUSH CONTACT STEP ATTENUATOR FOR COAXIAL CIRCUITS Filed March29, 1968 3 Sheets-Sheet 2 INVENTOR Helmut Bacher ATTORNEY Dec. 22, 1970H. BACHER 3,550,046

FLUSH CONTACT STEP ATTENUATOR FOR COAXIAL CIHCUITS Filed March 29, 19683 Sheets-Sheet 3 FIG. 6.

INVENTOR He /muf Bacher M Kz M ATTORNEY United States Patent Office3,550,046 Patented Dec. 22, 1970 3,550,046 FLUSH CONTACT STEP ATTENUATORFOR COAXIAL CIRCUITS Helmut Bacher, Arlington, Va., assignor toWeinsclel Engineering Co., Gaitlersburg, Md., a corporation of DelawareFiled Mar. 29, 1968, Ser. No. 717,285 Int. Cl. H01p 1/22 U.S. Cl. 333-814 Claims ABSTRACT OF THE DISCLOSURE A cylinder drum step attenuator forcoaxial cable microwave circuits, stepped by a full rotation cycle ofthe drive shaft in such fashion that during half of a rotaton cycle ofthe drive shaft the drum is held rigidly in position with one attenuatorin the circut, and during the next half turn of the shaft, the drum issmoothly rotated an amount sufficient to put the next attenuator intothe circuit.

This invention relates to step attenuators for microwave circuits, ofthe general type disclosed ir U.S. patent application Ser. No. 558,927,filed June 20, 1966, for Flush Contact Step Attenuator, by Bacher et al.The invention 'elates to an improved drive for this type of attenuator,the drive comprising a modified Geneva gear drive for stepping acylindrical drum-type attenuator so as to successively insert attenuatorelements mounted thereon into a coaxial circuit. Successive attenuatorsare stepped by successive full turns of the drive step, the mechanismbeing such that during half the turn the drum is rigidly held againstrotation, so that a selected attenuator is properly positioned in thecoaxial circut for connection thereto, and during the next half turn ofthe drive shaft, the drum is moved sufficiently to insert the nextattenuator into the circut, the motion being accomplished smoothly andgradually, being essentially a simple harmonic motion, which permits thedrive shaft to be motor driven, so that any desired attenuator can beput into the circut with extreme rapidity, even though this may requirestepping the attenuator drum through practically a complete cycle. Thedrum mechanism is simple and rugged, and easily machined by standardOperations, yet can readily be made to position a selected attenuatorwith great precision to hold it rigidly against any possibility ofdisplacement.

The specific nature of the invention, as well as other objects andadvantages thereof, will clearly appear from a description of apreferred embodiment as shown in the accompanying drawings, in which:

FIG. 1 is a plan View of an attenuator according to the invention;

FIG. 2 is an end view of the drum or cylinder mounting a set of steppedattenuators of dierent values for selective nsertion into the circut;

FIGS. 3A-3F are schematic drawings showings the relative position of thedrive shaft and driven drum element during a complete rotation cycle ofthe drive shaft;

FIG. 4 is a schematic View showing a motor-driven attenuator;

FIG. S is a sectonal View taken on line 5 -5 of FIG. 6; and

FIG. 6 is a top view of a modified form of the invention.

Referring to FIG. 1, the attenuator is mounted in a suitable box or yolk2 and comprises a cylindrical drum 3 rotatable on a shaft 4 which issupported in suitable bearngs in the yolk 2. The drum 3 is provided witha number of apertures 6 for holding attenuators, which are preferably ofthe same type as disclosed in the copendng application Ser. No. 558927above referred to. The attenuators 7 extend beyond the drum and areprovided with Contacts 8 and 9 adapted to engage stationary coaxialcontacts 11 and 12 respectively, which are preferably of the same flushtype as disclosed in the above-mentioned application. Conventionalcoaxial transmission line connectors 10 and -10a are provided forconnection to an external circuit. Thus, by rotating the drum 3 on itsaxis, successive attenuators can be engaged with the contacts 11 and 12,and thus put into the microwave circut associated with these terminals.In the prior application, a starwheel drive and detent arrangement wasemployed to rotate the cylinder 3 and thus to step the attenuator. Inthe present disclosure, a modified Geneva-gear arrangement is used tostep the attenuator, comprising a drive shaft 13, which may be manuallydriven by knob 14 as disclosed in FIG. 1, or may be motor driven asdisclosed by FIG. 4. Fixed to the end of shaft 13 is a disc 16, on theforward surface of which is fixed a ball 17 radially displaced from theaxis shaft 13 by substantially one-half of the distance which thecircumference of drum 3 must move in order to step from one attenuatorto the next. Also fixed to disc 16 is a smaller radial distance from thecenter of the shaft than ball 17 is a stop boss 18 having an outersurface which is semi-cylindrical in form. The inner surface of boss 18is cut away as shown at 19 to insure adequate clearance duringoperation, as will be explaned below, although in some cases the element18 could be one-half of a rigid cylindrical rod if desired.

One the surface of drum 3 there is an annular raised band 19 containinga series of grooves or Channels 21 spaced apart a distance correspondngto the desired stepping distance, and between the channels 21 there area series of circular cut out portions 22 having a generally cylindricalconfiguration and dimensioned to snugly receive the outer cylindricalsurface of stop boss 18.

As best seen in FIG. 1, assuming the kno'b 14 is turned so as to movethe ball 17 to the left, the ball will enter slot 21 at the top of thefigure, and as rotation continues for a half turn, the cylinder will berotated through one step, the relationshp being as shown in FIGS. 3B,3C, 3D and 3F, so that the drum is rotated for a sufiicient distance toengage the next successive attenuator with terminals 11 and 12. It willbe noted that just as the ball 17 is leaving the slot, and the positionshown in FIG. 3F, the stop boss 18 has engaged the cut-out 22sufficiently so that the drum is now immovable in either direction, andthis engagement of these two elements continues during the nexthalf-turn of the shaft 13 until the position shown in FIG. 3B isreached, when the stepping action is again initiated during the nexthalf-turn of the shaft. It is thus apparent that the shaft does not needto be positioned very accurately in order for the attenuator to beaccurately aligned with the coaxial terminals with which it is engaged.Furthermore, it will be noted that when the ball 17 enters channel 21,it does so moving out along the length of the channel, and thereforewith no sudden shock, and it leaves in the same manner. During the period of rotation represented by FIGS. 3B-3F, the drum is sped up andslowed down with essentially a simple harmonic motion, and thereforewith a minimum of Shock of sudden acceleration. This is of importance inthe case where it is desired to rapidly Shift from one attenuator to anyother selected attenuator, which may involve rotating the drum throughpractically a full revolution, in the case where a uni-directional motordrive is employed, which is the usual situation.

FIG. 4 shows a motor-driven arrangement for the attenuator, the motor 26being usually actuated by a selector circut, not shown because this isnot part of the pres ent invention but which is a well-knownarrangement, whereby a remote circut selector causes the motor to drivefor a sufiicient distance to put any selected attenua- 3 tor into thecircuit. In some cases, it is desired to do this within a fraction of asecond, and the motor must therefore be driven at high speed. Thepresent attenuator is well adapted to this use, due to theabove-described characteristics, since it can be driven at very highspeed without producing excessive shocks or strains in the system.

It will be noted that all the coacting elements of the above-describeddrive can be made by simple machining Operations using standardequipment.

F IGS. 5 and 6 show a linear step attenuatior Operating on the sameprinciple as FIGS. 1-4, except that the drum 3 is straightened out toform a linear element 3' which slides back and forth as knob 14' isturned. Corresponding elements are identified by the same referencenumbers as in FIGIS': 1-4, with a prime added, and except for the linearmotion, the action is the same as described above.

It will be apparent that the embodiments shown are only exemplary andthat various modifications can be made in Construction and arrangementwithin the scope of my invention as defined in the appended claims.

I claim:

1. A stepping device for coaXial conductor attenuating circuitscomprising (a) a rotatable cylindrical drum having equally spacedrecesses for holding attenuators,

(b) a yoke mounting said drum for rotation about its central axis,

(c) coaXial terminal means supoprted by said yoke in circuit conductivealignment with an attenuator mounted in one of said recesses,

(d) means for rotationally stepping said drum to successively andselectively present other attenuators respectively held in recesses intoconnective alignment with said terminal means,

(e) said last means (d) comprising a rotary drive shaft mounted at rightangles to the axis of said drum,

(f) a drive boss fixed to said shaft at an end thereof adjacent to thesurface of said drum, said boss being radially spaced from the axis ofsaid shaft and oriented for rotation in a plane perpendicular to theshaft and beyond its end,

(g) a stop boss fixed to said shaft in the plane of rotation of saiddrive boss and having a substantially semi-cylindrical stop surfacediametrically opposed to said drive boss and coaxial with said shaft,

(h) an annular raised band of the surface of said drum having a seriesof spaced longitudinal Channels lying parallel to the axis of the drumand cooperating With said drive boss during substantially one-half cycleof rotation of said drive shaft to move said drum one step during saidone-half cycle, said channels being spaced a distance corresponding totwice the radial 4- dstance of said drive boss from its center ofrotation,

(i) said annular band having circular cut-out portions between saidchannels to snugly receive said stop boss and cooperate with itscylindrical surface during the other half cycle of rotation of the driveshaft so as to prevent rotary movement of said drum during said otherhalf cycle,

(j) said terminal means being positioned so as to be in conductivecontact with an attenuator held by the drum when the stop channel isengaged at one of said cut-out portions.

2. The invention according to claim 1, said spaced recesses beingseparated by such a distance that attenuators held therein aresucessively presented into Contacting position with said terminalsduring successive full revolutions of said shaft.

3. The invention accordin to claim 1, said drive boss being in the formof a ball having a diameter slightly smaller than the width of anengaged channel.

4. The invention according to claim 1, and a series of gradedattenuators held in said spaced recesses of the drum for successiveengagement of said terminals.

References Cited UNITED STATES PATENTS 2,427,745 9/1947 Roger-Petit74-84 2,613,321 10/1952 Howard 325-464 3,046,499 7/1962 Waldick 333-81X3,219,953 11/1965 Schwartz 333-81 3,248,953 5/ 1966 Holper et al. 7410.l5 3,299,373 1/1967 Conney 333-81 2,44S,793 7/1948 Marchand 333-7FOREIGN PATENTS 594,142 11/ 1947 Great Britain 74-436 OTHER REFERENCESGeneva Design Permits Fast Index With Pause for Position Selection,Design News, July 1, 1956, Rogers Publishing Company, Englewood, Colo.,pp. 26-27.

The Elements of Mechanics and Mechanisms, Camm George Newnes Limited(Scientific Library, June 3, 1957), TJ145, pp 127, 128, and 134.

HERMAN KARL SAALBACH, Primary Examiner M. NUSSBAUM, Assistant ExaminerU.S. Cl. X.R. 333-7, 97

